Different filtration processes can be used to filter biological particles in a fluid. For example, the use of nanoporous aluminum oxide membranes is described in Ref. [1]. The membranes have a pore size between 70 and 15 nm and are fabricated by atomic layer deposition. The membranes are used together with centrifugation methods. Dielectrophoresis is used in Ref [2] within a microfluidic device, with a filtering efficiency of 97%. The device comprises two channels with several dielectrophoresis elements that separate and concentrate target particles. Ref [3] describes the use of surface-modified micropillars possessing affinity for bacterial cells, fabricated inside a PCR chip. Pillars with a square cross section are used for particle capture. Ref. [4] describes a lanthanum-based flocculation method coupled with a Mg2+-modified membrane filtration procedure. The flocculation step is applied to reduce the solution volume, followed by a two-step membrane filtration. One of the membrane steps comprises centrifugation.